Maintenance and related administration to support customer's service level agreements (SLA) are a large part of Operator's operational expenses (OpEx) for optical fiber networks. The labor and material costs for diagnosing maintenance problems within a fiber network can dominate Operator's budgets and impact customer's SLAs negatively. To manage these expenses, Operators have deployed redundant networks that have multiple links with automatic loss of link detection and switchover capabilities to insure SLAs and other mission critical services are maintained.
Usually when optical fibers are first deployed, highly skilled personnel with expensive fiber test equipment are assigned the task of ensuring and verify desired fiber plant loss budgets are met. This process of fiber plant deployment occurs before service is enabled to customers or during out-of-service periods, which are closely monitored and sometimes restricted due to customer's SLA constraints. All Long Haul, Metro and Access fiber optic based services are deployed in this manner.
Once a customer's service is enabled, Operators are responsible for the maintenance and servicing required by optical fiber links as they degrade over time. This places extra cost burden on the fiber plants to provide field testability. Typically this field testability requires extra splitters at ends of a fiber link to allow the connection of optical test equipment. Each additional splitter not only means more capital expense (CapEx) is incurred by the Operator but it also takes away precious dBs from the optical loss budget. Operators value greatly its fiber plant loss budgets where reach and other margin related policies are used to differentiate its service offerings at a fiber link level. Operators thus use non-traffic affecting optical test methods like Optical Time Domain Reflectometry (OTDR) using maintenance wavelengths of 1625 nm that is separate and independent from all other wavelengths used to carry customer service traffic. This is an expense capital and labor-intensive method for routine fiber maintenance checks while ensuring service outages do not occur.
Therefore performing In-Service OTDR maintenance procedure without the need for additional maintenance splitters and without the need for a separate maintenance wavelength is highly desirable to Operators due to realized OpEx, CapEx and Optical Loss budget savings.